The hydrocarbon which can react with sodium in liquid ammonia is

The compound ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{C}\equiv \mathrm{CH}$ contains hydrogen atom attached to triply bonded $\mathrm{sp}$ hybridized carbon which acquires acidic nature due to high electronegativity of carbon. This acetylinic hydrogen is replaced by ${\mathrm{Na}}^{+}$.

${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{C}\equiv \mathrm{CH}+\mathrm{Na}\to {\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{C}=\stackrel{-}{\mathrm{C}}:\mathrm{N}\stackrel{+}{\mathrm{a}}+\frac{1}{2}{\mathrm{H}}_2\mathrm{O}.$